Much of this unconstitutional legislation mirrors a bill Gov. Jay Nixon (D) vetoed last year. In September, Missouri’s overwhelmingly Republican senate came just one vote shy of the votes necessary to override Nixon’s veto. Like the bill Nixon vetoed last year, the new legislation contains a provision to arm public school personnel. It also would lower the minimum age to receive a concealed weapons permit from 21 to 19.

Few principles are more clearly established in American constitutional law than the prohibition on states nullifying federal laws. The Constitution provides that duly enacted federal laws “shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the constitution or laws of any state to the contrary notwithstanding.”

Indeed, it is particularly well established that states may not prosecute federal officials for carrying out their official duties. In the late Nineteenth Century, U.S. Supreme Court Justice Stephen Field (one of themost loathsome individuals ever to sit on the Supreme Court, although for reasons unrelated to this case) received death threats from a former colleague on the CaliforniaSupreme Court after Field decided a case adversely to the other man’s wife. Because of these threats, a United States Marshall named David Neagle was assigned to protect Field while he was traveling in California, and Neagle wound up shooting the man who threatened Field when that man made an attempt on Field’s life at a restaurant.

Although California charged Neagle with murder, the Supreme Court explained in In re Neagle that this is not allowed. As Neagel established, a federal official who “is held in custody in violation of the Constitution or a law of the United States, or for an act done or omitted in pursuance of a law of the United States. . . must be discharged.” Thus, the state of California was powerless to prosecute Neagle because he acted pursuant to his duties as a federal marshal.